Gondor was home to many Númenóreans. For it is indeed a much more fertile region than Arnor, in the north. Therefore the area was very populated even before the arrival of the sons of Elendil. At that time the main city of the region was not the famous Minas Tirith, or the capital Osgiliath but another city that we know as Pelargir. However Gondor was not truly a "nation", it had no sovereign right, it was born from the separation of Númenórian colonies and it's mainland, between Elendili (Friend of elves) and the king's men (These are Nùménorien who rebelled against the Valar by desire for immortality), though the colonies were occupied after the downfall of Akallabêth.

The young kingdom of gondor was ruled by Isildur and Anárion at first, while Arnor was led by Elednil (below). They all took part in the Last Alliance of Men and Elves that led to the first fall Sauron, which was followed by the subsequent occupation of Mordor throughout most of the Third Age. Let it be noted that Ilsildur, the man who cut the finger of Sauron and led the Alliance to victory is the brother of Anárion who is the ancestor of the Kings of Gondor. Isildur in turn generate the lineage of kings of Arnor, before his demise on the road northwards.

After the conflict, Gondor entered into a boom or millitary and economic power which continually increased. The power of the nation was such that it was during this time that major cities such as Minas Ithil whose name means the tower of Moon and that we know today as the Minas Morgul which means Tower of Sorcery saw their strength, prosperity and population grow. It was one of the two towers, along with Minas Anor, tower of the sun, which is now know as Minas Tirith, tower of the guard. Neither of these cities was the capital, which was in Osgiliath, upon the Anduin, in the middle of the kingdom between the two towers. It was during this period that the gondor began to rule over more and more territory as it's power grew and it's splendor began to mirror Númenoór of old. It's golden age was under the rule of King Hyarmendacil I ,which means "winner of the South", who was so powerful he foreced into vassalisation King Harad .